This application claims priority to Australian Application No. PR 0544, filed Sep. 28, 2000, which application is incorporated herein by specific reference.
1. The Field of the Invention
The present invention relates to a castored base for a chair. In particular, although not exclusively, the invention relates to a castored base for an office chair having a plurality of radiating legs, each supported by a respective castor. However, the present invention is not limited in its application to office chairs. The invention may also have application to other types of chairs such as domestic chairs, and also to tables, other moveable pieces of furniture and moveable office accessories.
2. The Relevant Technology
Office chairs are commonly provided with a wheeled base in the form of a central upright support column with a plurality of legs radiating from the lower end of the support column. Each of the legs is supported at its free end by a respective castor. The castors generally have two wheel portions which are rotatably mounted about a central body. The central body is provided with an upwardly extending connector pin extending above the two wheel portions. The connector pin is received by the end of the associated leg.
It will be appreciated that having the connector pin extending upwardly from above the two wheel portions dictates that the depth of each leg to receive the pin must be at least as deep as the length of the pin. Accordingly, this creates unnecessary bulk in the size of the legs, restricting free movement of the occupant""s legs under the seat portion. This is considered particularly disadvantageous since it has been found that occupants of office chairs commonly sit with their legs bent underneath the seat portion such that their feet are disposed approximately in line with their spinal column. Providing a correct posture is adopted, this is found to be a satisfactory ergonomic position. It will be appreciated that any castor arrangement which contributes to the bulk of the wheeled base, restricting free movement of the occupant"" feet will be annoying to the occupant.
Accordingly, it is an object of the present invention to provide an arrangement for a castor or castored base which overcomes or at least addresses some of the abovementioned disadvantages.
In accordance with an aspect of the present invention, there is provided a castored base for a chair including: a plurality of radially extending legs, each leg having a socket or sleeve fixed thereto adjacent an outer end thereof; and a castor connected to each socket or sleeve, each castor having two wheel portions and an axle assembly, the axle assembly including an axle to which the two wheel portions are rotatably mounted in spaced disposition and including a pin; wherein the pin of each castor is received in a respective one of the sockets or sleeves which extends at least in part between the two wheel portions.
The castored base may also be used to support a table or any other item of furniture or office accessory.
The pin may be releasably received in the respective socket or sleeve. The castored base may have a central upright support column with the plurality of legs radially extending from the lower end of the support column. Preferably, the radially extending legs extend in a substantially horizontal fashion. A small downward gradient may be incorporated as the legs extend radially outward. The legs may also incorporate a slight curve, preferably convex upwards.
In order to reduce their height, the legs are preferably of plate-like construction. Preferably, each leg incorporates a longitudinally extending strengthening web disposed on its underside. In a most preferred form of the invention, the strengthening web reduces in height in the radially outward direction along the associated leg.
Preferably, each socket or sleeve is an integrally formed part of the respective leg. Suitably, each pin is rotatably mounted within the respective socket/sleeve to rotate about an axis aligned with the longitudinal axis of the pin.
Each pin is preferably disposed centrally relative to the respective axle. Preferably, the longitudinal axis of the pin extends generally orthogonally to the longitudinal axis of the axle. The axes may be offset so that they do not intersect.
Accordingly, an intermediate portion may be provided as part of each axle assembly to extend between the axle and the pin. Preferably, the axle, the intermediate portion and the connector pin is an integrally formed component. The component may be cast, machined or forged.
Preferably, the pin in each castor is disposed substantially between the two wheel portions. Preferably, the top of the connector pin in its operable configuration extends no higher than level with the top of the wheel portions.
The axle assembly may include a body portion defining an aperture within which the axle is mounted. The body portion may include a plate having an annular boss defining the aperture, and a plurality of ribs extending radially outwardly from the boss.
Suitably, each wheel portion is circular in cross-section transverse to its rolling axis. Each wheel portion may have a rolling surface shaped as a cylinder or a hemisphere. In a most preferred form of the invention, each wheel portion has a rolling surface which is semi-ellipsoidal. In a most preferred form of the invention, each wheel portion is of solid, translucent plastic construction.
Each castor may further include a cover extending between the two wheel portions to at least partly close the gap therebetween. The cover may be an integral part of the axle assembly.
This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.